Masyu

Rules

Draw a single, non-intersecting loop that passes orthogonally through all circled cells. The loop must go straight through the cells with white circles, with a turn in at least one of the cells immediately before or after each white circle. The loop must make a turn in all the black circles but must go straight in both cells immediately before and after each black circle.

(Rules and example from PGP IB)

History of the puzzle

First appeared on Nikoli volume 90 (2000) under the name of "白真珠黒真珠" ("White pearls, black pearls"). Invented by アセトニトリル ("Acetonitril"). Renamed to "ましゅ" ("Masyu") in volume 103 (2003).

This puzzle was suggested as a modified version of "真珠の首飾り" ("Pearl earring") by 矢野龍王 ("Yano Ryuoh"), first appeared in 1999, where only white circles were present.

Variants

See List of Masyu variants.

Appearances in the past WPCs

Listed here are appearances of classic to almost-classic Masyus. For variants, see list of Masyu variants#Appearances in the past WPCs.

• WPC 2023/Round 15 (Triangular) by Takeya Saikachi
• WPC 2019/Round 3 (Permaculture hybrid with Yin Yang) by Silke Berendes
• WPC 2019/Round 11 (Cairo Pentagonal) by Christoph Seeliger
• WPC 2019/World Cup Playoffs by Erhard Notz
• WPC 2018/Round 7 by Jiří Hrdina
• WPC 2017/Round 3 by Prasanna Seshadri
• WPC 2017/Round 10 ("Optimizer") by Deb Mohanty
• WPC 2016/Round 2 by Matej Uher
• WPC 2016/Round 15 (part of a Matchmaker puzzle) by Matej Uher
• WPC 2015/Round 11
• WPC 2014/Round 3
• WPC 2014/Round 14
• WPC 2013/Part 1
• WPC 2013/Part 3 ("Digital")
• WPC 2013/Part 7